Power connections are typically made by AC power plugs that connect to appropriate receptacles. There are two basic classifications of plugs: straight-blade and locking. Both of these designs include exposed blades that fit into appropriate slots in a wall or cable receptacle. Straight-blade plugs are found nearly everywhere, and are intended for supplying light-duty, general purpose electrical devices with power. Twist-locking plug types are used for heavy industrial and commercial equipment, where increased protection against accidental disconnection is desired.
A drawback to conventional power plugs is that the blades of the straight-blade and locking plugs are fully exposed, and failures occur by arching across these exposed blades. In addition, the exposed blades can be damaged if not inserted correctly.